Rho0Finder/FindRho0 [ Subroutines ]

This routine implements a rho0 finding process as in experiments.
Given the list of detected particles in a specific event, it returns
aparticle list of (possible) reconstructed rho0.

If the particles have a detection probability less than 1, the
probability of the rho0 is the product of the two decay candidates.
One has the option to multiply this probability
with 1 minus the detection probability of every other
particle.

At the moment, this routine just implements the method used by
the Hermes experiment, cf. M.Tytgat, PhD thesis (Diffractive
production of rho0 and omega mesons at Hermes), p.116f.
A more general definition with some steering parameters (maybe
via jobCard) is anticipated.

This routine allocates memory for the rho0. Therefore it is necessary
that you clean up the particle list in the calling routine after use
via
call ParticleList_CLEAR(PartsOut,.true.)

In order to complete the Tytgat analysis, an additional cut on -t is
necessary

In order to get comparable results as in experiments, Kaons should
be instable in calculations and decay into pions.

We abuse many of the variables of the type to store information
different to their intention. We list them in the following:

Abuse: scaleCS --> probability, that the pions really come out
of a decay (1.0, if both pions are stored in
PIL_rho0Dec and 0.5, if only one pion is stored and 0, if we
constructed a rho0, which does not stem from a decay [or we forgot
to switch on storeRho0Info in collisionterm]).